Regular airtime: Sundays, 9pm ET

(Showtime)US: 26 Sep 2010

Dexter‘s fifth season picks up directly where the fourth left off: Dexter (Michael C. Hall) clutching his blood-soaked infant son.

His wife (Julie Benz) lies dead in the bathtub, As Dexter waits for the authorities to arrive, his eyes glaze and his shoulders slump. At first it’s unclear whether this serial killer shocked at his loss, or at the irony of the situation, namely, that Rita was murdered by a serial killer (last season’s guest star, John Lithgow). Unfortunately, the rest of the episode follows Dexter’s descent into a routine guilt spiral, blaming himself for Rita’s death (he should have “been there” to “protect her”), rather than ruminating on how it feels to be on this receiving end of a serial killing. How a series this smart could overlook the far more interesting angle is as much of a wasted opportunity as it is a disappointment.

Breaking the news to Rita’s other two children Astor (Christina Robinson) and Cody (Preston Bailey) proves especially difficult, as they are freshly returned from a trip to Disney World with their grandparents. With a Mickey Mouse hat on his head, Dexter coldly describes their mother’s murder to the children like he’s giving testimony in court. His efforts are awkward and stilted—and completely unaffecting.

If this all sounds rather grim, it is. And boring, too. The scene evinces none of the tension we expect, the tension that has suffused the series recently, as Dexter tips between his need to kill and his desire for domestic stability. On some level, we can imagine Dexter feels relief that Rita’s gone, as he’s spent years lying to her, but the series won’t entertain that possibility, leaning instead on his not-quite displayed grief, as if he’s like us. He ponders his lack of humanity and Rita’s enormous capacity to love. All true, but nothing new.

What does feel new is the turn for Dexter’s sister, Deborah (Jennifer Carpenter). Having spent too many seasons in dead-end relationships, she’s now finding an identity outside of men—except, of course, her brother, whose ostensible neediness demands her attention. While Dexter is mired in his own emotions, she’s looking after details, escorting him to the funeral home, keeping track of the kids, and even cleaning up the scene of the crime. She says she wants to be as good a sister to Dexter as he’s been a brother to her—as she still believes his lies. But she also sets some boundaries, resisting his suggestion that she take care of his baby, Harrison.

If Deborah can help Dexter with his family, she’s less able to help him maintain his lifelong cover. He refuses to cooperate with the FBI and insists on moaning about himself (“It was me!”) when talking about Rita’s death. Deb warns, “People will misunderstand you,” not seeing that he’s speaking at least a little bit of truth in such laments. Still, the potential plotting here is uninspired: while it’s understandable that Dexter feels a certain amount of guilt, his near-confessions seem a contrived way to gin up tension over whether a cop will take him seriously, and begin investigating his actual crimes. When he’s unable to function for Rita’s funeral, his seeming self-realization becomes untenable. If he’s suddenly feeling remorse that their entire relationship was predicated on his deceits, what he’s doing now doesn’t go a long way to show it.

Dexter has always treated death somewhat cavalierly. As we watch Dexter now, apparently sincerely unraveling over Rita’s death, we might be inclined to distrust his displays, or to feel that he’s finally feeling what his victims’ families have felt. The very idea of Dexter’s sincerity is particularly difficult to pull off (though Hall, who won a Golden Globe last year, again performs the role with unnerving elegance). Dexter’s core conflict is growing tiresome, as it’s changed so little from season to season. While Dexter may behave abhorrently, the series persists in making him sympathetic, witty and charming, if dishonest.

Dexter is also dishonest. It won’t present its central killer so that viewers ever have to contemplate their own pleasure in his brutality. Repeatedly lit from above, Dexter looks like he’s wearing a halo. It’s ironic, yes, but it’s also indicting the culture that produces and celebrates his cunning and his pathology. He is sometimes like us, in his sickness, but we never have to look at that.